I think I'm going to bet some real money on one of these two:
To answer the question about the transaction costs: They are negligible on any timeframe higher than M5 (when the spread chart is showing swings of 100 or more pips). I did some successful trades on lower timeframes already with GBPUSD vs. the others. GBPUSD and EURUSD vs. the others are producing the most interesting (nicely stationary) charts on lower timeframes.
The above two charts show swings of ca. 600 pips (1 on the y axis equals one yen (100 pips)).
To answer the question about the transaction costs: They are negligible on any timeframe higher than M5 (when the spread chart is showing swings of 100 or more pips). I did some successful trades on lower timeframes already with GBPUSD vs. the others. GBPUSD and EURUSD vs. the others are producing the most interesting (nicely stationary) charts on lower timeframes.
The above two charts show swings of ca. 600 pips (1 on the y axis equals one yen (100 pips)).